As said above, train to get more watts, fuel your workouts properly, your weight will end up wherever it needs to be.
If there are no hilly races around where you are then the good news is you’re going to have to learn to be extremely efficient and tactically astute to make the most of your watts on the flat! There’s a guy I’ve raced with who is about your size and pretty effective even on flat crit races. Extremely compact position allows him to get a lot of speed for his watts, he’s great at handling so maintains his speed well and makes up places during technical sections. When he’s tucked into a wheel he’s basically getting a completely free ride, and he can squeeze through gaps in the peloton. Put him in a bunch sprint finish when everybody is fresh and he’s going to struggle. But races rarely work out that way, and the more selective a race is and the more matches everybody has burned, the more likely he is to be in contention at the end. I’ve been in a 2 man break with him for 20km off the front of a crit race, it was absolutely brutal as on his pulls I was getting almost no recovery as there was minimal draft, whereas on my pulls he was getting a free ride! And had such a big draft benefit on my wheel that it would have been almost impossible to shake him off. Or at least doing so would have burned so many matches it would have wrecked my race.